Genetics and Cellular Function

Comprehensive vocabulary flashcards covering Chapter 4: Genetics and Cellular Function, including DNA/RNA structure, transcription, translation, DNA replication, the cell cycle, mitosis, and classical genetics principles.

Nucleotide

The monomer of nucleic acids, consisting of one sugar (deoxyribose in DNA), one phosphate group, and one nitrogenous base (either a purine or a pyrimidine).

Purines

Double-ring nitrogenous bases found in DNA and RNA, consisting of adenine (A) and guanine (G).

Pyrimidines

Single-ring nitrogenous bases; in DNA, these include cytosine (C) and thymine (T), while uracil (U) replaces thymine in RNA.

Law of Complementary Base Pairing

The rule stating that one strand of DNA dictates the base sequence of the other, where adenine pairs with thymine via $2$ hydrogen bonds, and cytosine pairs with guanine via $3$ hydrogen bonds.

Gene

An information-containing segment of DNA that codes for the production of a molecule of RNA that plays a role in synthesizing one or more proteins.

Genome

All the DNA in one $23$-chromosome set of an individual, consisting of an estimated $20,000$ to $25,000$ genes, where only about $2\%$ constitutes coding DNA and $98\%$ is noncoding DNA.

Genomics

The comprehensive study of the whole genome and how its genes and noncoding DNA interact to affect the structure and function of the whole organism.

Genetic Code

A system that enables four nucleotides to code for the amino acid sequence of all proteins using a minimum code of three nucleotides per amino acid.

Base Triplet

A sequence of three consecutive DNA nucleotides on the template strand that stands for one amino acid.

Codon

A $3$-base sequence in mRNA complementary to a DNA triplet; there are $64$ possible codons, $61$ of which code for amino acids.

Stop Codons

The three mRNA codons (UAG, UGA, and UAA) that signal the end of translation.

Start Codon

The mRNA codon AUG, which codes for methionine and initiates the amino acid sequence of a protein.

Genomic Medicine

The application of knowledge of the genome to the prediction, diagnosis, and treatment of disease, enabling early detection and expanding the potential for gene-substitution therapy.

Messenger RNA (mRNA)

A single-stranded RNA copy of a gene (often over $10,000$ bases) that carries the genetic code from the nucleus into the cytoplasm to be read by ribosomes.

Transfer RNA (tRNA)

A small single-stranded RNA molecule consisting of $70$ to $90$ bases that carries and delivers a specific amino acid to the ribosome during translation.

Ribosomes

Cytoplasmic granules composed of ribosomal RNA (rRNA) and enzymes that assemble amino acids into proteins according to the sequence of codons on mRNA.

Transcription

The process of copying genetic instructions from DNA to mRNA, occurring inside the nucleus.

RNA Polymerase

The enzyme that binds to DNA, opens the helix about $17$ base pairs at a time, and synthesizes a corresponding complementary pre-mRNA strand.

Exons

The functional 'sense' portions of immature pre-mRNA that are retained and spliced together to be translated into protein.

Introns

The noncoding 'nonsense' segments of immature pre-mRNA that must be removed by enzymes before translation.

Alternative Splicing

The process of removing introns and splicing together exons into different combinations, enabling a single gene to code for more than one protein.

Translation

The cellular process that converts the nucleotide sequence of mRNA into an amino acid sequence, occurring primarily in the cytoplasm on ribosomes.

DNA Helicase

An enzyme that unwinds and unzips a short segment of the DNA double helix during DNA replication, exposing its nitrogenous bases.

Replication Fork

The Y-shaped opening formed when DNA helicase separates the two complementary strands of DNA.

DNA Polymerase

The enzyme that reads exposed DNA bases at a rate of approximately $100\,\text{base pairs}/\text{second}$ and joins complementary free nucleotides to form a new daughter strand.

Semiconservative Replication

The process of DNA synthesis in which each resulting daughter DNA molecule contains one newly synthesized helix and one conserved parental helix.

Mutations

Changes in DNA nucleotide structure caused by replication errors or environmental mutagens such as radiation, viruses, and chemicals.

Cell Cycle

The life cycle of a cell extending from one division to the next, comprising interphase ($G_1$, $S$, and $G_2$ phases) and the mitotic ($M$) phase.

$G_1$ Phase

The first gap phase of the cell cycle; an interval between cell division and DNA replication during which the cell grows, performs normal metabolic functions, and accumulates materials for replication.

S Phase

The synthesis phase of the cell cycle during which DNA replication occurs and centrioles are duplicated.

$G_2$ Phase

The second gap phase of the cell cycle; an interval between DNA replication and division during which centriole duplication completes, cell division enzymes are synthesized, and DNA replication errors are repaired.

$G_0$ Phase

A resting state entered by cells that have left the cell cycle and no longer divide, such as mature muscle and nerve cells.

Mitosis

The process of nuclear division in somatic body cells, functioning in tissue growth, replacement of dead cells, repair of damaged tissues, and individual development from a zygote.

Prophase

The first phase of mitosis, characterized by chromosome condensation, nuclear envelope breakdown, centriole migration to opposite poles, and spindle fiber growth.

Metaphase

The second phase of mitosis, during which chromosomes align along the midline or equator of the cell and spindle fibers attach to kinetochores.

Anaphase

The third phase of mitosis, during which centromeres divide and spindle fibers pull sister chromatids apart toward opposite poles.

Telophase

The final stage of mitosis in which chromatids cluster at each pole, uncoil into chromatin, new nuclear envelopes and nucleoli form, and the mitotic spindle vanishes.

Cytokinesis

The division of the cytoplasm into two daughter cells, which overlaps with the final stages of nuclear division in telophase.

Contact Inhibition

The cessation of cell division that occurs when cells come into physical contact with other surrounding cells.

Karyotype

A chart of the $46$ chromosomes of a human cell laid out in order by size and other physical features.

Homologous Chromosomes

The two matching members of a chromosome pair that carry the same genes, with one chromosome inherited from each parent.

Autosomes

The $22$ pairs of human chromosomes that look alike, carry the same genes, and do not directly determine biological sex.

Sex Chromosomes

The single pair of chromosomes (XX in females, XY in males) that determines the genetic sex of an individual.

Diploid

Any cell containing $23$ pairs of chromosomes ($46$ chromosomes total), such as somatic body cells.

Haploid

Cells containing half the chromosome number of somatic cells ($23$ unpaired chromosomes), specifically sperm and egg cells (germ cells).

Gene Locus

The precise physical location of a particular gene on a chromosome.

Alleles

Different molecular versions or forms of a gene located at the same locus on homologous chromosomes.

Dominant Allele

An allele (denoted by an uppercase letter) whose phenotypic trait is detectable and masks the effect of any recessive allele present.

Recessive Allele

An allele (denoted by a lowercase letter) that is expressed in the phenotype only when present on both homologous chromosomes.

Genotype

The specific paired alleles an individual possesses for a given trait (either homozygous or heterozygous).

Phenotype

An observable physical or physiological characteristic of an individual resulting from the expression of their genotype.

Punnett Square

A grid diagram used to determine the expected genotypic and phenotypic ratios among offspring produced by a parental cross.

Gene Pool

The collective genetic makeup and totality of all alleles found across an entire population.

Multiple Alleles

A condition in which more than two allelic variants of a gene exist in the population, such as the $I^A$, $I^B$, and $i$ alleles responsible for ABO blood types.

Sex-Linked Traits

Hereditary characteristics carried on the sex chromosomes (X or Y) that tend to be inherited more frequently by one sex, such as red-green color blindness.